A tyre pressure monitoring sensor (TPMS) is an important device to a driver to ensure that the tyres of a vehicle are properly inflated in order to minimize the possibilities of any dangerous situations, especially during driving. Properly inflated tyres play a significant role in maximizing the fuel economy of the vehicle and performance and tyre life of the tyres. However, the tyre-wheel environment can be very hard on electronic products and pressure sensors, exposing them to harsh conditions such as temperature extremes, moisture, debris, and a variety of other potentially corrosive solvents and chemicals.
Therefore, careful TPMS package design is necessary to withstand temperature extremities and encompass all-inclusive media compatibility. The entire TPMS, including the electronics, housing, and mounting hardware, also needs to be lightweight in order to avoid an out-of-balance tyre/wheel. Furthermore, the TPMS should also be positioned at a robust location. The TPMS that is affixed onto the wheel (usually made of aluminum alloy or steel) rather than the tyre, allows the said TPMS to function independently of the tyre. For instance, changing a faulty TPMS would not require changing a new tyre and vice versa.
Currently, conventional TPMSs make use of two types of mounts on the wheel, namely valve mounts and mounting using steel bands, as shown in FIG. 1.
FIG. 1(a) shows a perspective view of the valve mount on a wheel 14. FIG. 1(b) shows the cross-sectional view of the sensor and electronics with the battery potted in a plastic package 10 and mounted to an air pressure valve 12 on the wheel 14. Disadvantages of the valve mount include air leaks (due to loss of residual torque on the sensor mount nut 16 to the wheel valve 12) and the breaking-off of the package 10 from the valve 12 (primarily due to road vibrations, but may also be due to the valve material used and the mount angle to the wheel 14). Additionally, torque profile control is difficult to maintain during the mounting of the plastic package 10 at the wheel supplier.
Another known method to mount a TPMS using a steel band is shown in FIG. 1(c), illustrating a cross-sectional view of the wheel 14. The tyre pressure sensor and RF transmitter with the battery is potted in a plastic housing 18 and then captured in a metal housing 20 that allows the passage of a steel band 22 wrapped around the wheel 14, with the ends of the steel band 22 joined by crimping. A two-sided self adhesive tape 24 may also be used primarily to position the metal housing 20 on the wheel 14 during the banding process, as shown in the exaggerated view of the dotted circle of FIG. 1(c), in FIG. 1(d). The primary method of mounting the tyre pressure sensor assembly is by the steel band 22 that counters the load from high-speed rotation (centripetal acceleration force) and vibrations/shocks from the road. The disadvantage of using a steel band 22 is the danger of the steel band 22 becoming loose at the joint, causing the plastic package 18 to be dismounted during high rotational forces. Furthermore, the assembly process for this design is cumbersome and involves high material and assembly costs.
It is also clear from both the mounting methods described above that physical damage to the plastic package 10 and 18 containing the sensor unit, may occur easily during mount and/or dismount of the tyre on the wheel 14.
Such sensor assemblies for both the said mounting methods are conventionally packed and shipped in dunnages, boxes or fixture nests from the manufacturer to the assembly plant.
Hence, it is accordingly an object of the present invention to provide a tyre pressure monitoring sensor (TPMS) secured or to be secured onto a wheel surface mainly by adhesive means which at least goes someway to addressing the abovementioned disadvantages or which will at least provide the public with a useful choice.